Coffee makers of the kind referred to herein are adapted to prepare a fresh coffee beverage fully automatically. Such coffee makers comprise a coffee bean container for receiving coffee beans to be ground, a grinder unit for grinding the coffee beans, and a brewing unit to which the freshly ground coffee powder is fed. In the brewing unit, the coffee powder is compressed and, thereafter, hot pressurized brewing water flows through the compressed coffee powder to extract a coffee beverage. Such coffee makers are also called “Espresso Coffee Machines” in general language use.
There is one particular problem in connection with these coffee makers, inasmuch as a lack of coffee beans in the grinder unit should be detected as soon as possible; otherwise, the drive motor of the grinder unit could overheat if it runs under no load conditions for a certain time. Another problem is seen in the fact that a relationship should be established to the amount of coffee beans already ground in the actual grinding cycle once the lack of coffee beans has been detected; thereby, after refilling coffee beans, the grinding cycle can be continued to grind only the remaining amount of coffee beans required to complement the already ground amount such that the correct total amount of coffee powder results that is required to brew a proper coffee beverage. Otherwise, the already ground amount of coffee would have to be discarded without having been used and replaced by a new, full charge of coffee powder.